Drinking water production by coagulation-microfiltration and adsorption-ultrafiltration

Microfiltration (MF) and ultrafiltration (UF) pilot plants were operated to produce drinking water from surface water from 1992 to 1996. Microfiltration was combined with pre-coagulation by polyaluminium chloride and was operated in a dead-end mode using hollow fiber polypropylene and monolith type ceramic membranes. Ultrafiltration pilot was operated in both cross-flow and dead-end modes using hollow fiber cellulose acetate membrane and was combined occasionally with powdered activated carbon (PAC) and granular activated carbon (GAC) adsorption. Turbidity in the raw water varied in the range between 1 and 100 mg/L (as standard Kaolin) and was removed almost completely in all MF and UF pilot plants to less than 0.1 mg/L. MF and UF removed metals such as iron, manganese and aluminium well. The background organics in the river water measured as KMnO4 demand varied in the range between 3 and 16 mg/L. KMnO4 demand decreased to less than 2 mg/L and to less than 3 mg/L on the average by the coagulation-MF process and the sole UF process, respectively. Combination of PAC or GAC adsorption with UF resulted in an increased removal of the background organics and the trihalomethanes formation potential as well as the micropollutants such as pesticides. Filtration flux was controlled in the range between 1.5 and 2.5 m/day with the trans-membrane pressure less than 100 kPa in most cases for MF and UF. The average water recovery varied from 99 to 85%. (C) 1998 Published by Elsevier Science Ltd